Gyrate atrophy (GA) of the choroid and retina is an autosomal recessive chorioretinal degeneration, caused by deficiency of the mitochondrial matri enzyme ornithine-delta-aminotransferase (OAT). This deficiency results in the accumulation of ornithine in the body fluids and leads to hyperornithinemia. Although the clinical phenotype is largely confined to the eye, OAT deficiency is a systemic disorder. With the final goal of applying gene therapy to this human genetic disease, we have established an in vitro model to test the correction of OAT enzymatic deficiency in mammalian cells, using OAT-recombinant retroviruses Herein, we report the construction of several Moloney murine leukemia virus (MoMLV)-based recombinant retrovirus vectors, in which the human OAT cDNA was placed under the transcriptional control of the mouse phosphoglycerate kinase (PGK) promoter or under the enhancer-promoter regulatory element derived from MoMLV long terminal repeat (LTR). The retrovirus constructs were packaged in the PG13-GALV cell line and used to transduce C9, an OAT-deficient cell line derived from Chinese hamster ovary cells (CHO-K1). We showed that the recombinant retrovirus transfers the hOAT gene into C9. Expression of the hOAT gene in the transduced C9- deficient cell line exceeded the level of endogenous human fibroblasts, OAT mRNA, and enzymatic activity.